For a given engine size and hardware, the maximum allowable peak cylinder firing pressure and turbine inlet (engine exhaust gas) temperature are generally defined during the component design process to limit engine operation below these threshold values. However, there is apparently no closed loop control strategy existing now to monitor and control these parameters during actual engine operation. Limiting engine operation within the allowable (pre-defined) peak firing cylinder pressure and turbine inlet temperature avoids excessive mechanical and thermal loads on the components and consequent damage to the engine.
Conceivably, one could monitor the peak firing cylinder pressure and turbine inlet temperature directly and change the engine operation such that the engine doesn't exceed these values. However, it is believed that no such control strategy exists or has been practiced. Furthermore, temperature sensors generally do not survive in such high temperatures and harsh environments for long periods of operation.
There are also turbocharged diesel engine operating conditions which produce a higher cylinder trapped oxygen content than is required for efficient combustion. Typically, this results in higher NOx production because of the resulting higher peak pressure in the cylinders and increased oxygen available to combine with free nitrogen.
It has been proposed to use a turbocharger compressor bypass system, controlled to bypass combustion air from the compressor to the inlet or outlet of the turbocharger turbine and thereby increase compressor air flow when needed to avoid compressor surge during certain transient engine operating conditions. An engine controller responds to signals indicating changes in atmospheric pressure, intake manifold pressure and engine speed to control a bypass valve and prevent the turbocharger from surging. However, a method and application of a compressor bypass system for controlling other engine conditions has apparently not been proposed.
A system and method for controlling cylinder peak firing pressure and turbine inlet temperature, and further controlling particular engine exhaust emissions is desired.